This invention relates to a process for translating data from one level of resolution to another, and more particularly relates to a process for mapping high resolution data into a lower resolution depiction.
During the past few years, a number of stylus activated personal computers and write input devices, such as signature capture and signature verification peripheral devices which may be used with retail or financial terminals or other business machines, have been introduced into the marketplace. These devices include some type of a digitizer for determining the coordinate location of a pen or stylus on an actual or simulated writing surface, as the operator inputs information by using the pen or stylus.
In a typical arrangement, a transparent digitizer is placed over a flat display panel, such as a liquid crystal display (LCD). As the operator writes on the digitizer using a stylus, the writing is digitized, processed and displayed on the LCD substantially simultaneously, as well as being transmitted to a utilizing device or stored in memory.
The quality of the digitized handwritten script or other indicia displayed on the display is determined by the resolution of the digitizer and the particular display used. In many instances, the resolution of the digitizer is much higher than the resolution of the display with the result that the resolution of the display becomes the limiting factor. However, the use of a relatively high-resolution display is not practical because of the higher cost of the display and the associated required video memory. In such situations, the use of a display of medium resolution is the practical alternative.
When using a display with a lower resolution than the resolution of the digitizer, the higher resolution digitizer data must first be downscaled to the display resolution before the data can be displayed. However, the uncertainty, due to electrical noise, in the high resolution data can pose a problem because of the larger quantization error at the lower resolution.
This problem is illustrated in FIG. 1A, where a few sampled points 12 of a typical straight-line segment 14 on a grid 16 are shown. Each square 18 on the grid represents a pixel on the display. The grid 16 is shown in a relatively large scale in order to illustrate the problem. Ideally the sampled points 12 should all be in a straight line as shown in FIG. 1B. However, as can be seen in FIG. 1A, the high resolution sample points 12 do not actually fall precisely in a straight line, due to the small unavoidable electrical noise in the analog signal. In addition, since the points fall along the boundary of two columns of pixels, the selected pixels 20, which are shaded in FIGS. 1A and 1B, do not represent a straight line in FIG. 1A, as they do in FIG. 1B. This phenomenon causes the signal noise to be greatly magnified at the lower resolution. It should be emphasized that no matter how small the noise level is, the above problem will still exist.
One solution to the above problem is to use digital filtering to reduce noise. However the problem will not be eliminated, since the uncertainty in the least significant bit (LSB) is reduced, but is not totally removed. Therefore the irregularity in the straight line can still occur, though less frequently. Also, the additional computations required for digital filtering may cause too much software overhead. Finally, any kind of digital filtering results in some finite time delay, depending on the order of the filter implemented; that is, some previous points are required for the computation of a new point.